Diabetes mellitus is a chronic disorder characterized by insulin deficiency, hyperglycemia, and high risk for development of complications of the eyes, kidneys, peripheral nerves, heart and blood vessels. The disease is highly prevalent, affecting as many as 16 million people in the U.S. The disease is also expensive, in terms of both human suffering and dollars; it is estimated that approximately 1 in every 7 health care dollars spent in the U.S. goes to diabetes care, mostly for treatment of the chronic complications. In the U.S., diabetes is the most common cause of blindness in young adults, kidney failure, and non-traumatic limb amputation.
The Diabetes Control and Complications Trial (DCCT), completed in 1993, showed that the risk for development and progression of the chronic complications of diabetes is closely related to the degree of glycemic control, as measured by glycated hemoglobin (GHb) determinations. The DCCT also provided a large body of data relating GHb values to mean blood glucose. Thus, the DCCT results have set the stage for establishing specific diabetes treatment goals using GHb as an index of mean blood glucose concentration.
Ideally, early detection of altered blood glucose levels would lead to careful monitoring and long term control of blood glucose concentrations. There is a need for a rapid and accurate assay for measuring blood glucose levels. Many current blood glucose monitoring tests are subject to recent food intake or other lifestyle habits that may cause short term glucose levels to fluctuate dramatically. These may not give an accurate view of trends in blood glucose levels and may mask elevated baseline levels. As mentioned, it has previously been established that elevated blood glucose leads to increased glycation of hemoglobin (Hb) in circulating erythrocytes and that the level of glycated Hb is correlated with the glucose levels over about a three month period. Therefore, recent food intake has little impact on the glycated Hb level, thus giving a more accurate level of mean glucose levels in the blood.
A variety of diagnostic assays and related devices have been developed for point-of-care (POC) testing. In view of the convenience of POC diagnostic assays and related devices, the timeliness of their results, and the high incidence of diabetes, the need for an early diagnostic test for discovery of predilection to diabetes, and also for monitoring therapy has emphasized the extraordinary need for a POC diagnostic test. This is best accommodated in non hospital environments and also in situations where phlebotomists are not required (i.e., there is no need for blood draws). Generally, POC devices may be portable or otherwise transportable. In some cases, they may even be handheld.
Further, because there is a lot of variability in the tests that are currently available, it would be desirable to provide POC systems that have high sensitivity, precision, accuracy, and reliability of measurement, and yet are readily available to large populations. The present invention describes a method of determining blood glucose levels by measuring the amount of glycated hemoglobin in a small sample of blood making use of chromatographic test strips in an assay system that is amenable to POC device configuration.